class Base:
def __init__(self):
self.x = 4
class C1(Base):
...
class C2(Base):
...
obj1 = C1()
obj2 = C2()
obj1.x = 2
I understand with "Singletons" if I change "self.x" of C1 it could automatically update "self.x" of every instance of that single class... but how would I update all classes using the same base?
Move the x declaration out of the init:
class Base:
x = 4
def __init__(self):
Later when you need to set it, do the following:
Base.x = 5
You could wrap this into a @staticmethod to make it easier as well.
As others have mentioned, static variables are really bad and you shouldn't use them unless it's your last resort.
Someone correct me if i'm wrong but this can be solved easily with a reaaaal simple descriptor so for example:
class KeepSync(object):
def __init__(self, default):
self.value = default
def __get__(self, instance, owner):
return self.value
def __set__(self, instance, value):
self.value = value
class Foo(object):
bar = KeepSync(0)
class C1(Foo):
pass
class C2(Foo):
pass
f = C1()
g = C2()
print "f.bar is %s\ng.bar is %s" % (f.bar, g.bar)
print "Setting f.bar to 10"
f.bar = 10
print "f.bar is %s\ng.bar is %s" % (f.bar, g.bar) # YAY BOTH ARE 10 !
Any object that inherits KeepSync descriptor will always return that value, i'm not sure if I helped but, that's how I understood the problem, you wouldn't even need a base class but you can
What you are trying to do won't work. While the initial x = 4 is stored on the class, not the instance, any assignment such as obj1.x = 2 will store it on the instance.
If you really want to create a singleton, (ab)use a metaclass to ensure that each instance created is actually the same one. See this answer for an example how to do it.
